The use of various materials incorporated into polymeric resins in order to improve the flame retardance thereof is known in the prior art. It is also known that the flame resistance of these polymers (e.g., polyesters) may be improved by including bound halogen therein. The bound halogen is included in the polymer (e.g., polyester) by use of halogen containing monomer or monomers used in the formation of the polymer. It is also known that the inclusion of phosphorus compounds or antimony compounds in these halogen containing polymers sometimes enhances the flame resistance of the product. Inorganic flame retardants such as antimony oxide (Sb.sub.2 O.sub.3) may be characterized as having a low solubility in the more volatile and desirable polymer solvents such as methylene chloride, chloroform, and dioxane which may be utilized in wet or dry spinning. Accordingly such additives have been utilized in spinning, extruding and molding operations. However, the polymer dopes containing these inorganic additives which may be processed to form articles by extrusion often exist as a heterogeneous system comprising small solid particles of the inorganic flame retardant additives. These solid particles tend to clog the extrusion orifice thereby interfering with the efficiency of the extrusion operation.
It has been observed that while the techniques used to reduce the flammability of polymeric resins do so to some extent, most suffer from some drawback. Compounds containing the phosphinate group have been utilized in the prior art as flame retardant additives as illustrated by U.S. Pat. Nos. 3,014,949, 3,574, 164 and 3,014,953.
However, the metal salts of phosphonic acid salts which appear in U.S. Pat. No. 3,574,164 are ionic, and would therefore not be soluble in organic solvents. Further, those phosphorus compounds which are monomeric, such as found in all of the cited patents, would not be expected to show enhanced thermal stability and would likely impart a plasticizer effect to most polymer systems.
The poly metal phosphinates of the presently claimed invention are polymeric nonionic coordination compounds and are soluble in organic solvents.
It is therefore an object of the present invention to provide a method of enhancing the fire retardancy of halogenated aromatic polymers of the type described herein.
It is another object of the present invention to provide a novel flame retardant halogenated aromatic polymeric composition.
It is a further object of the present invention to provide a flame retardant halogenated aromatic polymeric composition of enhanced thermal stability.
It is another object of the present invention to provide a novel flame retardant halogenated aromatic polyester composition.
It is a further object of the present invention to provide a flame retardant halogenated aromatic polyester composition of enhanced thermal stability.
It is still a further object of the present invention to provide a flame retardant additive of enhanced solubility over other known inorganic flame retardant additives in solvents encountered in spinning, molding, and extrusion operations.
It is another object of the present invention to provide a polymeric inorganic flame retardant additive that is soluble in a polymer melt and compatible with melt extrusion processing.
These and other objects as well as the scope, nature and utilization of the invention will be apparent to those skilled in the art from the following description and appended claims.